Background
Breast cancer survival rates in Europe have improved significantly over recent decades owing to advancements in screening and treatment methods. With an increasing number of women living for many years after diagnosis, understanding the influence of a breast cancer diagnosis on lifestyle behaviours, which are critical determinants of prognosis and comorbidity, is of utmost importance.
Objectives
The aim of this study is to compare changes in alcohol consumption, smoking, BMI, and physical activity (considered both individually and jointly through a Healthy Lifestyle Index) in women following a breast cancer diagnosis with those in breast cancer-free women within the European Prospective Investigation into Cancer and Nutrition (EPIC).
Materials and methods
We analysed complete-case data from 129,376 women aged 49 years on average at recruitment, who participated in the EPIC cohort, of whom 2,712 were diagnosed with invasive breast cancer between baseline (1992-1999) and follow-up (1996-2011), and 126,664 remained cancer-free. Lifestyle factors (alcohol, tobacco, BMI, and physical activity) were collected and combined into Healthy Lifestyle Indexes (HLIs) at both time points. Linear mixed-effects models were used to examine changes in HLI and its individual components between women diagnosed with breast cancer and those who remained cancer-free.
Results
Preliminary results show that a breast cancer diagnosis between baseline and follow-up was associated with a non-significant decrease in overall HLI score (β = –0.05; 95% CI: –0.12, 0.02) compared to cancer-free women. A small but statistically significant decrease in the BMI score was observed (β = –0.05; 95% CI: –0.07, –0.02) among women with a breast cancer diagnosis compared to cancer-free women. For other components of the HLI, the estimates were 0.01 (95% CI: -0.02;0.04) for smoking score, 0.02 (95% CI: -0.02;0.06) for alcohol score and -0.07 (95% CI: -0.07;0.02) for physical activity score. Additional analyses are ongoing to explore the impact of tumour characteristics (stage, ERPR status, …), menopausal status or socio-economic factors.
Conclusion
Breast cancer survivors exhibited only small variations in lifestyle modifications when compared to women without cancer during the same follow-up period, with the exception of BMI, which slightly shifted towards a less favourable value. These findings emphasise that guidelines and lifestyle interventions might be necessary following a diagnosis of breast cancer.